The Ruby banked array resource checks (initiated from SLICC) did a check and
allocate at the same time. If a transition needs more than one resource, then
it might check/allocate resource #1, then fail to get resource #2. Another
transition might then try to get the same resources, but in reverse order.
Deadlock.
This patch separates resource checking and resource reservation into two
steps to avoid deadlock.
It was previously possible for a stalled message to be reordered after an
incomming message. This patch ensures that any stalled message stays in its
original request order.
This patch adds a few helpful functions that allow .sm files to directly
invalidate all cache blocks using a trigger queue rather than rely on each
individual cache block to be invalidated via requests from the mandatory
queue.
This patch allows DPRINTFs to be used in SLICC state machines similar to how
they are used by the rest of gem5. Previously all DPRINTFs in the .sm files
had to use the RubySlicc flag.
This patch exposes the tag and data array latencies to the SLICC state machines
so that it can be used to determine the correct enqueue latency for response
messages.
To have multiple Entry types (e.g., a cache Entry type and
a directory Entry type), just declare one of them as a secondary
type by using the pair 'main="false"', e.g.:
structure(DirEntry, desc="...", interface="AbstractCacheEntry",
main="false") {
...and the primary type would be declared:
structure(Entry, desc="...", interface="AbstractCacheEntry") {
This patch fixes the type handling when prefix operations are used. Previously
prefix operators would assume a void return type, which made it impossible to
combine prefix operations with other expressions. This patch allows SLICC
programmers to use prefix operations more naturally.
This patches adds support for transitions of the form:
transition(START, EVENTS, *) { ACTIONS }
This allows a machine to collapse states that differ only in the next state
transition to collapse into one, and can help shorten/simplfy some protocols
significantly.
When * is encountered as an end state of a transition, the next state is
determined by calling the machine-specific getNextState function. The next
state is determined before any actions of the transition execute, and
therefore the next state calculation cannot depend on any of the transition
actions.
This patch allows SLICC protocols to use more than one message type with a
message buffer. For example, you can declare two in ports as such:
in_port(ResponseQueue_in, ResponseMsg, responseFromDir, rank=3) { ... }
in_port(tgtResponseQueue_in, TgtResponseMsg, responseFromDir, rank=2) { ... }
This patch was created by Bihn Pham during his internship at AMD.
There is no need to delay hit callback response messages by a cycle because
the response latency is already incurred in the Ruby protocol. This ensures
correct timing of memory instructions.
The Minor CPU currently doesn't drain properly when it is switched
out. This happens because Fetch 1 expects to be in the FetchHalted
state when it is drained. However, because the CPU is switched out, it
is stuck in the FetchWaitingForPC state. Fix this by ignoring drain
requests and returning DrainState::Drained from MinorCPU::drain() if
the CPU is switched out. This is always safe since a switched out CPU,
by definition, doesn't have any instructions in flight.
Minor currently activates thread 0 in startup() to work around an
issue where activateContext() is called from LiveProcess before the
process entry point is known. When activateContext() is called, Minor
creates a branch instruction to the process's entry point. The first
time it is called, the branch points to an undefined location (0). The
call in startup() updates the branch to point to the actual entry
point.
When instantiating a switched out Minor CPU, it still tries to
activate thread 0. This is clearly incorrect since a switched out CPU
can't have any active threads. This changeset adds a check to ensure
that the thread is active before reactivating it.
The drain refactor patches introduced a couple of bugs in the way
Minor handles draining. This patch fixes an incorrect assert and a
case of infinite recursion when the CPU signals drain done.
This patch removes the RequestCause, and also simplifies how we
schedule the sending of packets through the memory-side port. The
deassertion of bus requests is removed as it is not used.
This patch makes cache sets aware of the way number. This enables
some nice features such as the ablity to restrict way allocation. The
implemented mechanism allows to set a maximum way number to be
allocated 'k' which must fulfill 0 < k <= N (where N is the number of
ways). In the future more sophisticated mechasims can be implemented.
This patch changes how writebacks communicate whether the line is
passed as modified or owned. Previously we relied on the
isSupplyExclusive mechanism, which was originally designed to avoid
unecessary snoops.
For normal cache requests we use the sharedAsserted mechanism to
determine if a block should be marked writeable or not, and with this
patch we transition the writebacks to also use this
mechanism. Conceptually this is cleaner and more consistent.
Some minor fixes and removal of dead code. Changing the flags to be
enums rather than static const (to avoid any linking issues caused by
the latter). Also adding a getBlockAddr member which hopefully can
slowly finds its way into caches, snoop filters etc.
This adds a vector register type. The type is defined as a std::array of a
fixed number of uint64_ts. The isa_parser.py has been modified to parse vector
register operands and generate the required code. Different cpus have vector
register files now.
The Process class methods were using an improper style and this subsequently
bled into the system call code. The following regular expressions should be
helpful if someone transitions private system call patches on top of these
changesets:
s/alloc_fd/allocFD/
s/sim_fd(/simFD(/
s/sim_fd_obj/getFDEntry/
s/fix_file_offsets/fixFileOffsets/
s/find_file_offsets/findFileOffsets/
The patch clarifies whether file descriptors are host file descriptors or
target file descriptors in the system call code. (Host file descriptors
are file descriptors which have been allocated through real system calls
where target file descriptors are allocated from an array in the Process
class.)
This patch extends the previous patch's alterations around fd_map. It cleans
up some of the uglier code in the process file and replaces it with a more
concise C++11 version. As part of the changes, the FdMap class is pulled out
of the Process class and receives its own file.
This patch gets rid of unused Process::dup_fd method and does minor
refactoring in the process class files. The file descriptor max has been
changed to be the number of file descriptors since this clarifies the loop
boundary condition and cleans up the code a bit. The fd_map field has been
altered to be dynamically allocated as opposed to being an array; the
intention here is to build on this is subsequent patches to allow processes
to share their file descriptors with the clone system call.
This patch updates the x86 decoder so that it can decode instructions with vex
prefix. It also updates the isa with opcodes from vex opcode maps 1, 2 and 3.
Note that none of the instructions have been implemented yet. The
implementations would be provided in due course of time.
Multi gem5 is an extension to gem5 to enable parallel simulation of a
distributed system (e.g. simulation of a pool of machines
connected by Ethernet links). A multi gem5 run consists of seperate gem5
processes running in parallel (potentially on different hosts/slots on
a cluster). Each gem5 process executes the simulation of a component of the
simulated distributed system (e.g. a multi-core board with an Ethernet NIC).
The patch implements the "distributed" Ethernet link device
(dev/src/multi_etherlink.[hh.cc]). This device will send/receive
(simulated) Ethernet packets to/from peer gem5 processes. The interface
to talk to the peer gem5 processes is defined in dev/src/multi_iface.hh and
in tcp_iface.hh.
There is also a central message server process (util/multi/tcp_server.[hh,cc])
which acts like an Ethernet switch and transfers messages among the gem5 peers.
A multi gem5 simulations can be kicked off by the util/multi/gem5-multi.sh
wrapper script.
Checkpoints are supported by multi-gem5. The checkpoint must be
initiated by a single gem5 process. E.g., the gem5 process with rank 0
can take a checkpoint from the bootscript just before it invokes
'mpirun' to launch an MPI test. The message server process will notify
all the other peer gem5 processes and make them take a checkpoint, too
(after completing a global synchronisation to ensure that there are no
inflight messages among gem5).
This is another step in the process of removing global variables
from Ruby to enable multiple RubySystem instances in a single simulation.
The list of abstract controllers is per-RubySystem and should be
represented that way, rather than as a global.
Since this is the last remaining Ruby global variable, the
src/mem/ruby/Common/Global.* files are also removed.
This is another step in the process of removing global variables
from Ruby to enable multiple RubySystem instances in a single simulation.
With possibly multiple RubySystem objects, we can no longer use a global
variable to find "the" RubySystem object. Instead, each Ruby component
has to carry a pointer to the RubySystem object to which it belongs.
This patch begins the process of removing global variables from the Ruby
source with the goal of eventually allowing users to create multiple Ruby
instances in a single simulation. Currently, users cannot do so because
several global variables and static members are referenced by the RubySystem
object in a way that assumes that there will only ever be a single RubySystem.
These need to be replaced with per-RubySystem equivalents.
This specific patch replaces the global var g_ruby_start, which is used
to calculate throughput statistics for Throttles in simple networks and
links in Garnet networks, with a RubySystem instance var m_start_cycle.
Add a simple device shim that interfaces with the NoMali model
library. The gem5 side of the interface supports Mali T60x/T62x/T760
GPUs. This device model pretends to be a Mali GPU, but doesn't render
anything and executes in zero time.
The drain() call currently passes around a DrainManager pointer, which
is now completely pointless since there is only ever one global
DrainManager in the system. It also contains vestiges from the time
when SimObjects had to keep track of their child objects that needed
draining.
This changeset moves all of the DrainState handling to the Drainable
base class and changes the drain() and drainResume() calls to reflect
this. Particularly, the drain() call has been updated to take no
parameters (the DrainManager argument isn't needed) and return a
DrainState instead of an unsigned integer (there is no point returning
anything other than 0 or 1 any more). Drainable objects should return
either DrainState::Draining (equivalent to returning 1 in the old
system) if they need more time to drain or DrainState::Drained
(equivalent to returning 0 in the old system) if they are already in a
consistent state. Returning DrainState::Running is considered an
error.
Drain done signalling is now done through the signalDrainDone() method
in the Drainable class instead of using the DrainManager directly. The
new call checks if the state of the object is DrainState::Draining
before notifying the drain manager. This means that it is safe to call
signalDrainDone() without first checking if the simulator has
requested draining. The intention here is to reduce the code needed to
implement draining in simple objects.
Draining is currently done by traversing the SimObject graph and
calling drain()/drainResume() on the SimObjects. This is not ideal
when non-SimObjects (e.g., ports) need draining since this means that
SimObjects owning those objects need to be aware of this.
This changeset moves the responsibility for finding objects that need
draining from SimObjects and the Python-side of the simulator to the
DrainManager. The DrainManager now maintains a set of all objects that
need draining. To reduce the overhead in classes owning non-SimObjects
that need draining, objects inheriting from Drainable now
automatically register with the DrainManager. If such an object is
destroyed, it is automatically unregistered. This means that drain()
and drainResume() should never be called directly on a Drainable
object.
While implementing the new functionality, the DrainManager has now
been made thread safe. In practice, this means that it takes a lock
whenever it manipulates the set of Drainable objects since SimObjects
in different threads may create Drainable objects
dynamically. Similarly, the drain counter is now an atomic_uint, which
ensures that it is manipulated correctly when objects signal that they
are done draining.
A nice side effect of these changes is that it makes the drain state
changes stricter, which the simulation scripts can exploit to avoid
redundant drains.
The memWriteback() and memInvalidate() calls used to live in the
Serializable interface. In this series of patches, the Serializable
interface will be redesigned to make serialization independent of the
object graph and always work on the entire simulator. This means that
the Serialization interface won't be useful to perform maintenance of
the caches in a sub-graph of the entire SimObject graph. This
changeset moves these memory maintenance methods to the SimObject
interface instead.
The drain state enum is currently a part of the Drainable
interface. The same state machine will be used by the DrainManager to
identify the global state of the simulator. Make the drain state a
global typed enum to better cater for this usage scenario.
When the Python helper code switches CPU models, it sometimes also
needs to change the memory mode of the simulator. When this happens,
it accidentally tried to drain the simulator despite having done so
already. This changeset removes the redundant drain.
Serialize pixels as unsigned 32 bit integers by adding the required
to_number() and stream operators. This is used by the FrameBuffer,
which now implements the Serializable interface. Users of frame
buffers are expected to serialize it into its own section by calling
serializeSection().
Events expected to be unserialized using an event-specific
unserializeEvent call. This call was never actually used, which meant
the events relying on it never got unserialized (or scheduled after
unserialization).
Instead of relying on a custom call, we now use the normal
serialization code again. In order to schedule the event correctly,
the parrent object is expected to use the
EventQueue::checkpointReschedule() call. This happens automatically
for events that are serialized using the AutoSerialize mechanism.
Objects that are can be serialized are supposed to inherit from the
Serializable class. This class is meant to provide a unified API for
such objects. However, so far it has mainly been used by SimObjects
due to some fundamental design limitations. This changeset redesigns
to the serialization interface to make it more generic and hide the
underlying checkpoint storage. Specifically:
* Add a set of APIs to serialize into a subsection of the current
object. Previously, objects that needed this functionality would
use ad-hoc solutions using nameOut() and section name
generation. In the new world, an object that implements the
interface has the methods serializeSection() and
unserializeSection() that serialize into a named /subsection/ of
the current object. Calling serialize() serializes an object into
the current section.
* Move the name() method from Serializable to SimObject as it is no
longer needed for serialization. The fully qualified section name
is generated by the main serialization code on the fly as objects
serialize sub-objects.
* Add a scoped ScopedCheckpointSection helper class. Some objects
need to serialize data structures, that are not deriving from
Serializable, into subsections. Previously, this was done using
nameOut() and manual section name generation. To simplify this,
this changeset introduces a ScopedCheckpointSection() helper
class. When this class is instantiated, it adds a new /subsection/
and subsequent serialization calls during the lifetime of this
helper class happen inside this section (or a subsection in case
of nested sections).
* The serialize() call is now const which prevents accidental state
manipulation during serialization. Objects that rely on modifying
state can use the serializeOld() call instead. The default
implementation simply calls serialize(). Note: The old-style calls
need to be explicitly called using the
serializeOld()/serializeSectionOld() style APIs. These are used by
default when serializing SimObjects.
* Both the input and output checkpoints now use their own named
types. This hides underlying checkpoint implementation from
objects that need checkpointing and makes it easier to change the
underlying checkpoint storage code.
All x87 misc registers are implemented in an array of 64 bit values
but in real hardware the size of some of these registers is smaller.
Previsouly all 64 bits where incorrectly set and then later read. To
ensure correctness we mask the value in setMiscRegNoEffect to write
only the valid bits.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
This patch drops the NetworkMessage class. The relevant data members and functions
have been moved to the Message class, which was the parent of NetworkMessage.
The accessor function getDestination() for Destination variable in the
coherence message clashes with the getDestination() that is part of the Message
class. Hence the name change.
This structure's only purpose was to provide a comparison function for
ordering messages in the MessageBuffer. The comparison function is now
being moved to the Message class itself. So we no longer require this
structure.
This patch increases the default read/write buffer sizes for the DDR4
controller config to values that are more suitable for the high
bandwidth and high bank count.
This patch updates the command arbitration so that bank group timing
as well as rank-to-rank delays will be taken into account. The
resulting arbitration no longer selects commands (prepped or not) that
cannot issue seamlessly if there are commands that can issue
back-to-back, minimizing the effect of rank-to-rank (tCS) & same bank
group (tCCD_L) delays.
The arbitration selects a new command based on the following priority.
Within each priority band, the arbitration will use FCFS to select the
appropriate command:
1) Bank is prepped and burst can issue seamlessly, without a bubble
2) Bank is not prepped, but can prep and issue seamlessly, without a
bubble
3) Bank is prepped but burst cannot issue seamlessly. In this case, a
bubble will occur on the bus
Thus, to enable more parallelism in subsequent selections, an
unprepped packet is given higher priority if the bank prep can be
hidden. If the bank prep cannot be hidden, the selection logic will
choose a prepped packet that cannot issue seamlessly if one exist.
Otherwise, the default selection will choose the packet with the
minimum bank prep delay.
This patch adds a simple lookup structure to avoid iterating over the
write queue to find read matches, and for the merging of write
bursts. Instead of relying on iteration we simply store a set of
currently-buffered write-burst addresses and compare against
these. For the reads we still perform the iteration if we have a
match. For the writes, we rely entirely on the set. Note that there
are corner-cases where sub-bursts would actually not be mergeable
without a read-modify-write. We ignore these cases and opt for speed.
This patch changes how the crossbar classes deal with
responses. Instead of forwarding responses directly and burdening the
neighbouring modules in paying for the latency (through the
pkt->headerDelay), we now queue them before sending them.
The coherency protocol is not affected as requests and any snoop
requests/responses are still passed on in zero time. Thus, the
responses end up paying for any header delay accumulated when passing
through the crossbar. Any latency incurred on the request path will be
paid for on the response side, if no other module has dealt with it.
As a result of this patch, responses are returned at a later
point. This affects the number of outstanding transactions, and quite
a few regressions see an impact in blocking due to no MSHRs, increased
cache-miss latencies, etc.
Going forward we should be able to use the same concept also for snoop
responses, and any request that is not an express snoop.
This patch takes the final step in removing the is_top_level parameter
from the cache. With the recent changes to read requests and write
invalidations, the parameter is no longer needed, and consequently
removed.
This also means that asymmetric cache hierarchies are now fully
supported (and we are actually using them already with L1 caches, but
no table-walker caches, connected to a shared L2).
WriteInvalidateReq ensures that a whole-line write does not incur the
cost of first doing a read exclusive, only to later overwrite the
data. This patch splits the existing WriteInvalidateReq into a
WriteLineReq, which is done locally, and an InvalidateReq that is sent
out throughout the memory system. The WriteLineReq re-uses the normal
WriteResp.
The change allows us to better express the difference between the
cache that is performing the write, and the ones that are merely
invalidating. As a consequence, we no longer have to rely on the
isTopLevel flag. Moreover, the actual memory in the system does not
see the intitial write, only the writeback. We were marking the
written line as dirty already, so there is really no need to also push
the write all the way to the memory.
The overall flow of the write-invalidate operation remains the same,
i.e. the operation is only carried out once the response for the
invalidate comes back. This patch adds the InvalidateResp for this
very reason.
This patch adds two new read requests packets:
ReadCleanReq - For a cache to explicitly request clean data. The
response is thus exclusive or shared, but not owned or modified. The
read-only caches (see previous patch) use this request type to ensure
they do not get dirty data.
ReadSharedReq - We add this to distinguish cache read requests from
those issued by other masters, such as devices and CPUs. Thus, devices
use ReadReq, and caches use ReadCleanReq, ReadExReq, or
ReadSharedReq. For the latter, the response can be any state, shared,
exclusive, owned or even modified.
Both ReadCleanReq and ReadSharedReq re-use the normal ReadResp. The
two transactions are aligned with the emerging cache-coherent TLM
standard and the AMBA nomenclature.
With this change, the normal ReadReq should never be used by a cache,
and is reserved for the actual (non-caching) masters in the system. We
thus have a way of identifying if a request came from a cache or
not. The introduction of ReadSharedReq thus removes the need for the
current isTopLevel hack, and also allows us to stop relying on
checking the packet size to determine if the source is a cache or
not. This is fixed in follow-on patches.
This patch adds a parameter to the BaseCache to enable a read-only
cache, for example for the instruction cache, or table-walker cache
(not for x86). A number of checks are put in place in the code to
ensure a read-only cache does not end up with dirty data.
A follow-on patch adds suitable read requests to allow a read-only
cache to explicitly ask for clean data.
This patch adds eviction notices to the caches, to provide accurate
tracking of cache blocks in snoop filters. We add the CleanEvict
message to the memory heirarchy and use both CleanEvicts and
Writebacks with BLOCK_CACHED flags to propagate notice of clean and
dirty evictions respectively, down the memory hierarchy. Note that the
BLOCK_CACHED flag indicates whether there exist any copies of the
evicted block in the caches above the evicting cache.
The purpose of the CleanEvict message is to notify snoop filters of
silent evictions in the relevant caches. The CleanEvict message
behaves much like a Writeback. CleanEvict is a write and a request but
unlike a Writeback, CleanEvict does not have data and does not need
exclusive access to the block. The cache generates the CleanEvict
message on a fill resulting in eviction of a clean block. Before
travelling downwards CleanEvict requests generate zero-time snoop
requests to check if the same block is cached in upper levels of the
memory heirarchy. If the block exists, the cache discards the
CleanEvict message. The snoops check the tags, writeback queue and the
MSHRs of upper level caches in a manner similar to snoops generated
from HardPFReqs. Currently CleanEvicts keep travelling towards main
memory unless they encounter the block corresponding to their address
or reach main memory (since we have no well defined point of
serialisation). Main memory simply discards CleanEvict messages.
We have modified the behavior of Writebacks, such that they generate
snoops to check for the presence of blocks in upper level caches. It
is possible in our current implmentation for a lower level cache to be
writing back a block while a shared copy of the same block exists in
the upper level cache. If the snoops find the same block in upper
level caches, we set the BLOCK_CACHED flag in the Writeback message.
We have also added logic to account for interaction of other message
types with CleanEvicts waiting in the writeback queue. A simple
example is of a response arriving at a cache removing any CleanEvicts
to the same address from the cache's writeback queue.
This patch fixes an issue which is very wide spread in the codebase,
causing sporadic linking failures. The issue is that we declare static
const class variables in the header, without any definition (as part
of a source file). In most cases the compiler propagates the value and
we have no issues. However, especially for less optimising builds such
as debug, we get sporadic linking failures due to undefined
references.
This patch fixes the Request class, by turning the static const flags
and master IDs into C++11 typed enums.
All the object loaders directly examine the (already completely loaded
by object_file.cc) memory image. There is no current motivation to
keep the fd around.
This patch updates the compiler minimum requirement to gcc 4.7 and
clang 3.1, thus allowing:
1. Explicit virtual overrides (no need for M5_ATTR_OVERRIDE)
2. Non-static data member initializers
3. Template aliases
4. Delegating constructors
This patch also enables a transition from --std=c++0x to --std=c++11.
Remove the assert when adding a port to the RubyPort retry list.
Instead of asserting, just ignore the added port, since it's
already on the list.
Without this patch, Ruby+detailed fails for even the simplest tests
Snoop packets share the request pointer with the originating
packets. We need to ensure that the snoop packet destruction does not
delete the request. Snoops are used for reads, invalidations,
HardPFReqs, Writebacks and CleansEvicts. Reads, invalidations, and
HardPFReqs need a response so their snoops do not delete the
request. For Writebacks and CleanEvicts we need to check explicitly
for whethere the current packet is an express snoop, in whcih case do
not delete the request.
There seems to have been a debug print left in when the original ARMv8
support was merged in. This printout is performed every time you
initialize a hardware thread, and it prints raw pointers, so it always
causes diffs in the regression. This patch removes the debug print.
The flush() method in CircleBuf resets the state of the circular
buffer, but fails to set size to zero. This obviously confuses code
that tries to determine the amount of data in the buffer. Set the size
to zero on flush.
Fixes missed forward eviction to CPU. With the O3CPU this can lead to load-load
reordering, as the LQ is never notified of the invalidate.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
A single HMC-2500 x32 model based on:
[1] DRAMSpec: a high-level DRAM bank modelling tool developed at the University
of Kaiserslautern. This high level tool uses RC (resistance-capacitance) and CV
(capacitance-voltage) models to estimate the DRAM bank latency and power
numbers.
[2] A Logic-base Interconnect for Supporting Near Memory Computation in the
Hybrid Memory Cube (E. Azarkhish et. al) Assumed for the HMC model is a 30 nm
technology node. The modelled HMC consists of a 4 Gbit part with 4 layers
connected with TSVs. Each layer has 16 vaults and each vault consists of 2
banks per layer. In order to be able to use the same controller used for 2D
DRAM generations for HMC, the following analogy is done: Channel (DDR) => Vault
(HMC) device_size (DDR) => size of a single layer in a vault ranks per channel
(DDR) => number of layers banks per rank (DDR) => banks per layer devices per
rank (DDR) => devices per layer ( 1 for HMC). The parameters for which no
input is available are inherited from the DDR3 configuration.
put O_DIRECT under ifdefs -- this fixes build for MacOSX.
Also use correct class for arm64 openFlagTable.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
This changeset adds support for aarch64 in kvm. The CPU module
supports both checkpointing and online CPU model switching as long as
no devices are simulated by the host kernel. It currently has the
following limitations:
* The system register based generic timer can only be simulated by
the host kernel. Workaround: Use a memory mapped timer instead to
simulate the timer in gem5.
* Simulating devices (e.g., the generic timer) in the host kernel
requires that the host kernel also simulates the GIC.
* ID registers in the host and in gem5 must match for switching
between simulated CPUs and KVM. This is particularly important
for ID registers describing memory system capabilities (e.g.,
ASID size, physical address size).
* Switching between a virtualized CPU and a simulated CPU is
currently not supported if in-kernel device emulation is
used. This could be worked around by adding support for switching
to the gem5 (e.g., the KvmGic) side of the device models. A
simpler workaround is to avoid in-kernel device models
altogether.
This changeset adds a GIC implementation that uses the kernel's
built-in support for simulating the interrupt controller. Since there
is currently no support for state transfer between gem5 and the
kernel, the device model does not support serialization and CPU
switching (which would require switching to a gem5-simulated GIC).
There are cases (particularly when attaching GDB) when instruction
events are scheduled at the current instruction tick. This used to
trigger an assertion error in kvm. This changeset adds a check for
this condition and forces KVM to do a quick entry that completes any
pending IO operations, but does not execute any new instructions,
before servicing the event. We could check if we need to enter KVM at
all, but forcing a quick entry is makes the code slightly cleaner and
does not hurt correctness (performance is hardly an issue in these
cases).
This changeset moves the ARM-specific KVM CPU implementation to
arch/arm/kvm/. This change is expected to keep the source tree
somewhat cleaner as we start adding support for ARMv8 and KVM
in-kernel interrupt controller simulation.
--HG--
rename : src/cpu/kvm/ArmKvmCPU.py => src/arch/arm/kvm/ArmKvmCPU.py
rename : src/cpu/kvm/arm_cpu.cc => src/arch/arm/kvm/arm_cpu.cc
rename : src/cpu/kvm/arm_cpu.hh => src/arch/arm/kvm/arm_cpu.hh
This patch changes how the address range calculates intersection such
that a system can have a number of non-overlapping interleaved ranges
without complaining. Without this patch we end up with a panic.
The MinorCPU would count bubbles in Execute::issue as part of
the num_insts_issued and so sometimes reach the instruction
issue limit incorrectly.
Fixed by checking for a bubble in one new place.
A step towards removing RubyMemoryControl and shift users to
DRAMCtrl. The latter is faster, more representative, very versatile,
and is integrated with power models.
There are cases when we don't want to use a system register mapped
generic timer, but can't use the SP804. For example, when using KVM on
aarch64, we want to intercept accesses to the generic timer, but can't
do so if it is using the system register interface. In such cases,
we need to use a memory-mapped generic timer.
This changeset adds a device model that implements the memory mapped
generic timer interface. The current implementation only supports a
single frame (i.e., one virtual timer and one physical timer).
The ArmSystem class has a parameter to indicate whether it is
configured to use the generic timer extension or not. This parameter
doesn't affect any feature flags in the current implementation and is
therefore completely unnecessary. In fact, we usually don't set it
even if a system has a generic timer. If we ever need to check if
there is a generic timer present, we should just request a pointer and
check if it is non-null instead.
The generic timer model currently does not support virtual
counters. Virtual and physical counters both tick with the same
frequency. However, virtual timers allow a hypervisor to set an offset
that is subtracted from the counter when it is read. This enables the
hypervisor to present a time base that ticks with virtual time in the
VM (i.e., doesn't tick when the VM isn't running). Modern Linux
kernels generally assume that virtual counters exist and try to use
them by default.
This changeset cleans up the generic timer a bit and moves most of the
register juggling from the ISA code into a separate class in the same
source file as the rest of the generic timer. It also removes the
assumption that there is always 8 or fewer CPUs in the system. Instead
of having a fixed limit, we now instantiate per-core timers as they
are requested. This is all in preparation for other patches that add
support for virtual timers and a memory mapped interface.
The register dumping code in kvm tries to print the bytes in large
registers (128 bits and larger) instead of printing them as hex. This
changeset fixes that.
Some versions of the kernel incorrectly swap the red and blue color
select registers. This changeset adds a workaround for that by
swapping them when instantiating a PixelConverter.
Currently, frame buffer handling in gem5 is quite ad hoc. In practice,
we pass around naked pointers to raw pixel data and expect consumers
to convert frame buffers using the (broken) VideoConverter.
This changeset completely redesigns the way we handle frame buffers
internally. In summary, it fixes several color conversion bugs, adds
support for more color formats (e.g., big endian), and makes the code
base easier to follow.
In the new world, gem5 always represents pixel data using the Pixel
struct when pixels need to be passed between different classes (e.g.,
a display controller and the VNC server). Producers of entire frames
(e.g., display controllers) should use the FrameBuffer class to
represent a frame.
Frame producers are expected to create one instance of the FrameBuffer
class in their constructors and register it with its consumers
once. Consumers are expected to check the dimensions of the frame
buffer when they consume it.
Conversion between the external representation and the internal
representation is supported for all common "true color" RGB formats of
up to 32-bit color depth. The external pixel representation is
expected to be between 1 and 4 bytes in either big endian or little
endian. Color channels are assumed to be contiguous ranges of bits
within each pixel word. The external pixel value is scaled to an 8-bit
internal representation using a floating multiplication to map it to
the entire 8-bit range.
The bitmap generation code is hard to follow and incorrectly uses the
size of an enum member to calculate the size of a pixel. This
changeset cleans up the code and adds some documentation.
The processes of warming up and cooling down Ruby caches are simulation-wide
processes, not just RubySystem instance-specific processes. Thus, the warm-up
and cool-down variables should be globally visible to any Ruby components
participating in either process. Make these variables static members and track
the warm-up and cool-down processes as appropriate.
This patch also has two side benefits:
1) It removes references to the RubySystem g_system_ptr, which are problematic
for allowing multiple RubySystem instances in a single simulation. Warmup and
cooldown variables being static (global) reduces the need for instance-specific
dereferences through the RubySystem.
2) From the AbstractController, it removes local RubySystem pointers, which are
used inconsistently with other uses of the RubySystem: 11 other uses reference
the RubySystem with the g_system_ptr. Only sequencers have local pointers.
Three minor issues are resolved:
1. Apparently gcc 5.1 does not like negation of booleans followed by
bitwise AND.
2. Somehow the compiler also gets confused and warns about
NoopMachInst being unused (removing it causes compilation errors
though). Most likely a compiler bug.
3. There seems to be a number of instances where loop unrolling causes
false positives for the array-bounds check. For now, switch to
std::array. Potentially we could disable the warning for newer gcc
versions, but switching to std::array is probably a good move in
any case.
The system class currently clears the vector of active CPUs in
initState(). CPUs are added to the list by registerThreadContext()
which is called from BaseCPU::init(). This obviously breaks when the
System object is initialized after the CPUs. This changeset removes
the offending clear() call since the list will be empty after it has
been instantiated anyway.
The current ignoreWarnOnceFunc doesn't really work as expected,
since it will only generate one warning total, for whichever
"warn-once" syscall is invoked first. This patch fixes that
behavior by keeping a "warned" flag in the SyscallDesc object,
allowing suitably flagged syscalls to warn exactly once per
syscall.
Sometimes, we need to defer an express snoop in an MSHR, but the original
request might complete and deallocate the original pkt->req. In those cases,
create a copy of the request so that someone who is inspecting the delayed
snoop can also inspect the request still. All of this is rather hacky, but the
allocation / linking and general life-time management of Packet and Request is
rather tricky. Deleting the copy is another tricky area, testing so far has
shown that the right copy is deleted at the right time.
We currently assume that all uncacheable memory accesses are strictly
ordered. Instead of always enforcing strict ordering, we now only
enforce it if the required memory type is device memory or strongly
ordered memory.
The Request::UNCACHEABLE flag currently has two different
functions. The first, and obvious, function is to prevent the memory
system from caching data in the request. The second function is to
prevent reordering and speculation in CPU models.
This changeset gives the order/speculation requirement a separate flag
(Request::STRICT_ORDER). This flag prevents CPU models from doing the
following optimizations:
* Speculation: CPU models are not allowed to issue speculative
loads.
* Write combining: CPU models and caches are not allowed to merge
writes to the same cache line.
Note: The memory system may still reorder accesses unless the
UNCACHEABLE flag is set. It is therefore expected that the
STRICT_ORDER flag is combined with the UNCACHEABLE flag to prevent
this behavior.
With the recent patches addressing how we deal with uncacheable
accesses there is no longer need for the work arounds put in place to
enforce certain sections of memory to be uncacheable during boot.
This patch takes a last step in fixing issues related to uncacheable
accesses. We do not separate uncacheable memory from uncacheable
devices, and in cases where it is really memory, there are valid
scenarios where we need to snoop since we do not support cache
maintenance instructions (yet). On snooping an uncacheable access we
thus provide data if possible. In essence this makes uncacheable
accesses IO coherent.
The snoop filter is also queried to steer the snoops, but not updated
since the uncacheable accesses do not allocate a block.
This patch simplifies the overall CPU by changing the TLB caches such
that they do not forward snoops to the table walker port(s). Note that
only ARM and X86 are affected.
There is no reason for the ports to snoop as they do not actually take
any action, and from a performance point of view we are better of not
snooping more than we have to.
Should it at a later point be required to snoop for a particular TLB
design it is easy enough to add it back.
This patch ensures that we pass on information about a packet being
shared (rather than exclusive), when forwarding a packet downstream.
Without this patch there is a risk that a downstream cache considers
the line exclusive when it really isn't.
This patch adds a missing counter update for the uncacheable
accesses. By updating this counter we also get a meaningful average
latency for uncacheable accesses (previously inf).
This patch changes the cache implementation to rely on virtual methods
rather than using the replacement policy as a template argument.
There is no impact on the simulation performance, and overall the
changes make it easier to modify (and subclass) the cache and/or
replacement policy.
This patch fixes a recent issue with gcc 4.9 (and possibly more) being
convinced that indices outside the array bounds are used when
initialising the FUPool members.
Both open_adaptive and close_adaptive page polices keep the page
open if a row hit is found. If a row hit is not found, close_adaptive
page policy precharges the row, and open_adaptive policy precharges
the row only if there is a bank conflict request waiting in the queue.
This patch makes the checks for above conditions simpler.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
Currently, each op class has a parameter issueLat that denotes the cycles after
which another op of the same class can be issued. As of now, this latency can
either be one cycle (fully pipelined) or same as execution latency of the op
(not at all pipelined). The fact that issueLat is a parameter of type Cycles
makes one believe that it can be set to any value. To avoid the confusion, the
parameter is being renamed as 'pipelined' with type boolean. If set to true,
the op would execute in a fully pipelined fashion. Otherwise, it would execute
in an unpipelined fashion.
This patch sets the default latency of the division microop to a single cycle
on x86. This is because the division instructions DIV and IDIV have been
implemented as loops of div microops, where each microop computes a single bit
of the quotient.
Same exception is raised whether division with zero is performed or the
quotient is greater than the maximum value that the provided space can hold.
Divide-by-Zero is the AMD terminology, while Divide-Error is Intel's.
This patch introduces a UFS host controller and a UFS device. More
information about the UFS standard can be found at the JEDEC site:
http://www.jedec.org/standards-documents/results/jesd220
Note that the model does not implement the complete standard, and as
such is not an actual implementation of UFS. The following SCSI
commands are implemented: inquiry, read, read capacity, report LUNs,
start/stop, test unit ready, verify, write, format unit, send
diagnostic, synchronize cache, mode select, mode sense, request sense,
unmap, write buffer and read buffer. This is sufficient for usage with
Linux and Android.
To interact with this model a kernel version 3.9 or above is
needed.
This adds a NAND flash timing model. This model takes the number of
planes into account and is ultimately intended to be used as a
high-level performance model for any device using flash. To access the
memory, use either readMemory or writeMemory.
To make use of the model you will need an interface model
such as UFSHostDevice, which is part of a separate patch.
At the moment the flash device is part of the ARM device tree since
the only use if the UFSHostDevice, and that in turn relies on the ARM
GIC.
This patch adds an I2C bus and base device. I2C is used to connect a
variety of sensors, and this patch serves as a starting point to
enable a range of I2C devices.
This patch fixes a few small issues to ensure gem5 compiles when using
gcc 5.1.
First, the GDB_REG_BYTES in the RemoteGDB header are, rather
surprisingly, flagged as unused for both ARM and X86. Removing them,
however, causes compilation errors as they are actually used in the
source file. Moving the constant into the class definition fixes the
issue. Possibly a gcc bug.
Second, we have an unused EthPktData constructor using auto_ptr, and
the latter is deprecated. Since the code is never used it is simply
removed.
The o3 cpu instruction queue model uses the count variable to track the number
of unissued instructions in the queue. Previously, the squash method used
this variable to avoid executing the doSquash method when there were no
unissued instructions in the pipeline. A corner case problem exists when
only issued instructions exist in the pipeline and a squash occurs; the
doSquash code is not invoked and subsequently does not clean up state properly.
